Tumor biopsies are often used for diagnostic purposes and for obtaining information on potentially effective therapies. For example, patients likely to respond to particular drugs can be identified by analyzing gene expression levels or patterns of tumor cells. The underlying mutations responsible for tumor growth can be characterized. In a number of tests tumor derived RNA is used as a starting material for the analysis, for example using reverse transcriptase polymerase chain reaction (RT-PCR). Unfortunately however, RNA is known to be particularly unstable.
As it is not always possible to do all necessary tests immediately after obtaining the tumor sample, such as a biopsy, a method of storing the sample is needed. In some cases the necessity for certain tests only becomes clear after some time or new tests are available which one would like to use for the analysis of previous tumors. It would be desirable to store tumor biopsies over an extended period of time.
Several approaches have thus been developed to store tumor cell samples. One method allowing RT-PCR amplification of RNA is deep freezing cells or tissue by immersing it in liquid nitrogen, and storing it at −80° C. To prevent degradation of RNA by RNases, the tissue must be homogenized in the frozen state before being mixed with RNA extraction buffer. With its stringent requirement for liquid nitrogen, the method is labour intensive and unsuitable for preserving tissue samples obtained in a clinical setting.
Often, pathological samples are formalin-fixed and paraffin-embedded (FSPE). These samples can be used for histological analysis, but analysis of RNA poses a problem. Special methods have been developed to extract RNA from such tissues, for example the method developed by K. Dannenberg et al. (U.S. Pat. No. 6,248,535 and U.S. Pat. No. 6,428,963). Again, the method of storage of tumor cells and retrieval of RNA or DNA is a very labour intensive.
Storage in water allows immunohistological analysis of proteins, but RNA is quickly degraded.
One of the standard methods for storage of tumor cells, such as tumor biopsies, uses the liquid composition RNAlater, commercially available from Ambion or Qiagen. As described in U.S. Pat. No. 6,528,64.1, this RNA preservation medium precipitates the RNA in the sample along with the sample protein and thus protects it from RNases. The precipitation is caused by high salt concentrations, typically ammonium sulfate.
RNAlater is not only suitable for extracting and afterwards analyzing RNA from tissues (W-H. Wang et al. (2001), Molecular Vision, vol. 7:89-94), but it is also suitable for storing tissue samples that have to be analyzed histologically or immunohistochemically (S. R. Florell et al. (2001), Mod. Pathol., vol. 14(2):116-128). However, these approaches directly kill the cells in the sample to be stored.
Preserving the viability of the cells would be useful, for example for overcoming limitations of the size of the tissue sample taken. Taking cells into culture would allow to proliferate the same. It would then also be possible to perform assays for biological functions of the cells at a later timepoint, either directly from the culture or after freezing and thawing the cells for further cultivation.
Preservation of viability is of supreme importance for the storage of organs for transplantation. It has been recognized that some of the solutions developed for the perfusion and storage of organs could also be suitable for preserving tissues or culturing cells. For example, U.S. Pat. No. 5,599,659 discloses that a chemically defined cell culture medium, comprising, e.g. retinal-derived fibroblast growth factor, cyclodextrin and chondroitin sulfate, can be used for the preservation of organs or tissues or the culture of vascular endothelial cells.
WO93/09220 refers to a defined basic culture medium with optional addition of growth promoting agents like hem, hemin, IL-3, SCF, EPO, IGF or retinoids that can be used for the mainentance and growth of hematopoetic progenitor cells or leukemia cells.
U.S. Pat. Nos. 6,004,579 and 6,495,532 propose to use liquid compositions comprising liposomes with lysophosphatidic acids for the inhibition of apoptosis. However, these compositions are not ideal for storing tumor cells and have further draw-backs, e.g. the uptake of phospholipids into tissues.
Further, organs on the one hand and healthy or pathological tissue samples and cells on the other differ in their requirements for oxygen and the partial oxygen pressure needed to maintain viability of organs could well damage tissue samples or cells. The problem underlying the present invention thus resides in providing easy and efficient methods for storing tumor cells, which methods enable the analysis of the tumor cells after storage.
The Present Invention
The present invention thus provides a method for storing cells, wherein the cells are stored in a composition comprising a base nutritive medium and liposomes at temperatures in a range of minus 196° C. to 37° C., characterized in that the liposomes comprise one or more sterols and that the cells are tumor cells.
The present inventors have surprisingly found that tumor cells can be stored for extended time periods in a base nutritive medium comprising liposomes comprising one or more sterols without essentially damaging the cells or degrading the RNA and/or DNA therein. The method of the present invention has the specific advantage that tumor cells, such as tumor biopsies can be stored in a single composition at room temperature for several days and even weeks. Tumor biopsies obtained from a patient may thus be stored and analyzed for extended time periods. Tumor biopsies may even be stored in the same composition in the frozen state. This will allow the preparation of tumor biopsy libraries, which can be used for drug target identification and various pharmaceutical research purposes. The preparation of a tumor library will for example allow to correlate the response of a patient treated with a certain drug treatment with a detailed molecular analysis of the tumor sample. This will significantly simplify the optimal treatment strategy for other patients with the same tumor type.
The cells can be stored in the composition in accordance with the methods of the present invention for any period of time, but are preferably stored for a period from at least one or several days up to several years.
According to a specifically preferred embodiment of the present invention the cells can be stored in the present method in such a manner that the RNA and/or DNA in the cells is essentially not degraded during storage. This will allow full analysis of the expression pattern of the tumor cells and classification of the tumor type. In accordance with the present application, the term “the RNA and/or DNA in the cells is essentially not degraded during storage” means that a comparison of the respective molecule type in cells after storage with the cells before storage shows that more than 60% of the RNA and/or DNA can still be analyzed. It is for example possible to analyze the tumor sample quality before storage by analysis of the concentration of a certain RNA, such as RNA encoding a known housekeeping gene expressed in the tissue of interest, via RT-PCR. After storage the test is repeated. The RNA is essentially not degraded during storage in accordance with the use of this term in the present application, when the analysis reveals that the amplification product after storage amounts to at least 60% preferably at least 80% of the amplification product before storage.
Alternatively or additionally the protein expression profile of the cells may be analyzed using any of the large number of methods for analyzing proteins known in the art. Again it is preferred that the proteins are not substantially degraded during storage. The cells may further be analyzed via histological staining or in situ hybridization after storage.
According to an especially preferred embodiment of the present invention the tumor cells can be stored in such a manner that they are still capable of proliferation after storage. For this purpose, the tumor cells can be isolated from the tissue if necessary and can be propagated according to well known techniques in a cell culture medium. The composition used for storing of tumor cells can advantageously also be used for propagation of tumor cells.
According to one aspect of the present invention, the method for storing cells comprises steps, wherein the cells are first stored in the composition at room temperature and subsequently stored in said composition at a temperature in a range of −196 to 0° C. According to a further preferred embodiment the cells are stored in the composition at room temperature for 1 to 14 days and subsequently stored in said composition at a temperature in a range of −196 and 0° C. for at least one month, preferably several years, wherein the RNA and/or DNA in the cells are not essentially degraded during storage. During storage at room temperature the composition may be exchanged when the nutrients are exhausted, such as every 3 days, which will enhance the viability of the cells.
In a further aspect, this invention provides a method for freezing cells of any cell type and storing them in frozen state, wherein the cells are frozen in a composition comprising a base nutritive medium and liposomes, characterized in that the liposomes comprise one or more sterols. Freezing cells immediately in this composition is possible without substantially affecting the viability of the cells, probably because the composition inhibits or reduces cristallisation in the cells. For this reason no additives like DMSO or HES have to be added to the composition to preserve the viability of the cells during freezing or thawing, which makes the method especially suitable when toxicity of DMSO would be problematic, e.g. with sensitive cells.
Therefore, the composition preferably does not contain a cryoprotective agent, such as HES (Hydroxyethylstarch), Glycerol, Arabinogalactan, DMSO (Dimethylsulfoxide) or ethylene glycol. Preferably, the composition is free from sera or undefined proteins.
In a preferred embodiment, before freezing, the cells are stored at room temperature in the composition for up to one week or up to 72 hours. Alternatively, the cells can also be stored at 4° C. before freezing.
The cells can be frozen or thawed by the methods commonly used by the person skilled in the art. Although a special freezing of thawing protocol is thus not necessary for carrying out the method of the invention, the cells are preferably frozen over 60 minutes (min) to −120° C. and then transferred to liquid nitrogen. In a preferred embodiment, the cells are frozen with the following freezing protocol, using a computer-controlled cold block: First, the tissue is held for 15 min at 4° C., thereafter, frozen at a rate of −99° C./min to −5° C., with −0.5° C./min to −7° C., with −30° C./min to −60° C., with 8,4° C./min to −18° C., held at −18° C. for 3 min, frozen with −2° C./min to −40° C., with −4° C./min to −80° C., with −10° C. to −120° C. and thereafter in liquid nitrogen to temperatures between −170° C. and −196° C.
Preferably, the temperature for long-term storage of the cells in the composition is −170° C. to −196° C. Cells are preferably stored in liquid nitrogen, e.g., in “Biosafe” cryotanks.
In accordance with the present invention the term “base nutritive medium” refers to a composition comprising amino acids, salts, vitamins, nucleotides, carbohydrates and/or anti-oxidants. The base nutritive medium will typically be a liquid composition.
The medium used in the methods of the present invention may additionally contain any number of compounds which are also suitable for storing tumor cells. Specifically it is preferred that the medium comprises one or more antimicrobial agents and/or growth factors. According to a further preferred embodiment the growth factors comprise epithelial growth factor, hepatocyte growth factor, platelet derived epithelial growth factor and/or vascular endothelial growth factor. The composition preferably does not contain any lysophosphotidic acids.
Liposomes in a water-based solution, as mentioned above, are present as lipid vesicles with a concentric lipid bilayer surrounding a hydrophilic core (Ed.: Falbe, Regitz, Römpp-Chemie-Lexikon, 1990, Georg Thieme Verlag, Stuttgart).
The liposomes in the composition used in the methods of the present invention comprise one or more sterols. Preferably, the sterols comprise cholesterol.
According to a specifically preferred embodiment the methods of the present invention are carried out using the Liforlab composition, containing the substances as described in tables 1-4 below.
The tumor cells may be any tumor cell such as tumor cells derived from a tumor cell line or a tumor tissue, such as a tumor biopsy or a tumor explant. According to a preferred embodiment the tumor cells are a tumor biopsy.
The tumor cells are preferably derived from a human or a mammal and the tumor is preferably a solid tumor, such as a melanoma or a renal cell, stomach, breast, oesophagus or colon carcinoma.
According to a further preferred embodiment, the method of the present invention comprises steps, wherein                (a) a tumor biopsy is derived from a human;        (b) the biopsy is stored in a composition comprising liposomes comprising cholesterol at room temperature for 1 to 14 days; and        (c) the biopsy is subsequently stored in the said composition at a temperature in the range of −196 and 0° C. for at least 1 month, preferably several years;        and wherein the RNA and/or DNA in the cells is essentially not degraded during storage. Preferably, the cells are still capable of proliferation after storage.        
This way of proceeding allows a specifically advantageous collection of tumor biopsies directly after explantation, forwarding of the tumor biopsies via courier or regular mail (at room temperature) to a diagnostic laboratory and/or long term storage of the tumor biopsy in the frozen state as well as analysis of the tumor type for correlating the tumor type to the patient response to a certain drug treatment.
A further advantage of such storage is that it would make genomic and proteomic analysis of tumor samples in comparison to the complementary non-tumor tissue of the same individuum possible. Non-tumor tissue can either be from a fresh biopsie or it can be stored in parallel with the tumor sample.
According to a further aspect the present invention is directed to the use of a composition for storing cells, wherein the composition comprises a base nutritive medium as defined above and liposomes characterized in that the liposomes comprise one or more sterols and that the cells are tumor cells.
In a further aspect, the present invention is directed to a composition comprising tumor cells, a base nutritive medium and liposomes which liposomes comprise one or more sterols. The tumor cells in this composition are preferably tumor biopsies.
According to a preferred embodiment, the composition comprises tumor biopsies, liposomes which comprise cholesterol and one or more growth factors, preferably epithelial growth factor, hepatocyte growth factor, platelet derived epithelial growth factor and/or vascular endothelial growth factor, and a base nutritive medium which comprises amino acids, salts, vitamins, nucleotides, carbohydrates, anti-oxidants.
In a related aspect, the invention is directed to a library of tumor biopsies comprising a number of different biopsies in a compositios as defined above stored in separate containers.
The present invention is further directed to the use of a respective library of tumor biopsies for diagnostic screening methods, drug efficacy validation and/or in methods for identifying anti-tumor drug targets.
For example, cells from the library of tumor biopsies could be thawed, taken into culture and implanted in nude mice. Thus, they would be available for drug screening, on one hand, to test if certain drugs are effective with this particular tumor, and on the other hand, to screen a library of potential active substances against certain tumors. A drug would be considered to be effective against the tumor, e.g. if the growth of the tumor is slowed, the number of metastases is lower or the tumor regresses partly or totally in a significant percentage of mice as compared with control animals not treated with the drug.
According to this embodiment, the invention is directed to a process for the preparation of a pharmaceutical composition for the treatment of tumor, comprising the use of tumors biopsies from a library of tumor biopsies according to claim 28 for screening of active anti-tumor substances and formulating the active substance thus identified with suitable pharmaceutical additives or carriers to obtain a pharmaceutical composition.
In a general aspect the present invention provides the use of a two-phase liquid composition for storing and stabilizing tumor tissue, wherein the first phase of the liquid composition comprises a base nutritive medium and the second phase comprises liposomes. The base nutritive medium comprises physiologically compatible concentrations of water-soluble or dispersible nutrients and physiological salts, for example amino acids, salts, vitamins, nucleotides, carbohydrates and anti-oxidants. The liposomes of the second phase are nanoparticles which comprise sterols, preferably cholesterol, and, optionally, fatty acids and cellular growth factors. The supposed structure of the liposomes comprises an outer lipophilic coating and an inner hydrophilic core.
The two phase composition used in the invention has an osmolality of at least about 300 mOsM/kg. Preferably, the two phase composition has an osmolality ranging from about 385 to 425 mOsM/kg. The pH of the two phase composition preferably is from about 7.2 to about 7.4. The nanoparticles preferably have a mean diameter ranging from about 100 nm to about 300 nm, more preferably from about 100 nm to about 200 nm.
The composition used in the invention can contain trace elements, simple carbohydrates, buffers, plasma volume expanders, energy substrates, xanthine oxidase inhibitors and the like, dissolved or dispersed in aqueous medium.
In a preferred embodiment, the base nutritive medium includes, in physiologically suitable concentrations, salts, water soluble vitamins, amino acids and nucleotides. These may include, simply by way of example, and without limitation, adenosine and its phosphates, uridine and its phosphate, other nucleotides and deoxynucleotides; B vitamins, e.g., B1, B2, B6, B12, biotin, inositol, choline, folate, and the like; vitamin coenzymes and cofactors, e.g. nicotinamide and fIavin adenine dinucleotides, and their respective phosphates, coenzyme A and the like; various physiological salts and trace minerals, e.g. salts of sodium, potassium, magnesium, calcium, copper, zinc and iron; the essential amino acids, although all twenty naturally-occurring amino acids, and/or derivatives thereof, are optionally included. The base medium also includes e.g. pH buffers, such as phosphate buffers and N-2-hydroxyethyl-piperazine-N′-2-ethanesulfonic acid (“HEPES”) buffer; simple sugars, e.g., glucose; osmotic enhancers, such as any suitable dextran, mannose and the like; as well as optional miscellaneous components, such as allopurinol, chondrotin, cocarboxylase, physiological organic acids, e.g. pyruvate, and optionally, a nutritive extract from natural sources, e.g., a yeast vitamin extract.
Thus, the base nutritive medium contains numerous nutrient and mineral factors at concentrations analogous to those found in blood, serum, plasma and/or normal body tissues, although certain of these are not natural blood components.
Optionally, the composition used in the invention can further include antimicrobial agents, such as antibiotics, antibacterials, specific antibodies and/or other known agents for controlling microbial contamination in organs, tissues and/or cells. Most known antimicrobials are referenced, in detail, by Goodman & Gilman's, The pharmacological basis of therapeutics, 10th ed., McGraw Hill, especially chapters 43 to 51.
The composition may further contain anti-coagulant, thrombolitic and/or antiplatelet drugs, e.g. heparin and related glycosaminoglycans, dicumarol, phenprocoumon, acenocoumarol and ethyl biscoumacetate, indandione, and derivatives thereof, and aspirin and dipyridamole, and the like. Non-steroidal antiinflammatory agents are also optionally included.
In one alternative embodiment, vitamin C (ascorbate) is optionally included in physiological or higher than physiological concentrations.
Many commercially available cell or tissue culture media products that are free of undefined proteins or animal sera can be adapted to serve as the base nutritive medium or starting point for preparation of the inventive composition, provided that such media are compatible with the specific requirements of the use of the composition.
The second phase of the composition is a liquid-aqueous emulsion comprising liposomes or nano-scale particles that are supposed to have a lipophilic outer layer and a hydrophilic core. Generally, the second phase includes lipophilic components able to form and stabilize the outer, lipophilic layer, including, for example, cholesterol, posphatidylcholine, vitamin E, cod liver oil, etc. Additional components include lipid-based energy sources, including physiologically compatible amounts of free fatty acids.
Preferably, the liposomes of the two phase composition comprise free fatty acids selected from the group consisting of oleic acid, linoleic acid, palmitic or stearic acid, myristic acid, lauric acid, eicosapentaenoic acid, docosahexaenoic acid, and combinations thereof.
Preferably, the two phase composition does not comprise a pharmaceutically significant quantity of phosphatidic acid or sugar, or lysophosphotidic acid or sugar.
In another preferred embodiment, the second phase includes hydrophilic supportive endocrine factors such as hydrocortisone, thyroxine, or its derivatives, and the like. Further supportive components include cellular growth factors, e.g. epithelial and endothelial growth factors, including physiolgically compatible amounts of vascular endothelial growth factor, platelet derived endothelial growth factor, epithelial growth factor, hepatocyte growth factor, platelet derived-endothelial growth factor, and the like. Optionally, other factors contemplated to be included in the second phase include inter-cellular messengers such as prostaglandins, e.g. prostaglandin E1. Preferably, physiologically compatible surfactants and detergents are also included, e.g. one or more water-soluble surfactant, preferably an amphiphilic block copolymer with a molecular weight of several thousand Daltons, such as a polypropyleneoxide-polyethyleneoxide block copolymer surfactant (e.g. Pluronic F-68; from BASF) and/or nonionic surfactants. Suitable nonionic surfactants include, e.g. polyoxyethylene derivatives of sorbitol esters, e.g. polyoxyethylene sorbitan monooleate surfactants that are commercially available as TWEEN® (Atlas Chemical Co.). TWEEN 80® is particularly preferred.
Oxygen that is supposed to be associated with the liposomes plays an important role in keeping up the metabolism of the cells. Of note, even though no additional step of enrichment with oxygen is necessary for the methods of the present invention, such enrichment could be beneficial for enhancing the viability of tumor cells, especially those with a high rate of proliferation or a high metabolic turnover. The content of oxygen comprised in the composition can thus be optimised for different tumors.
Oxygen can be enriched by bubbling air or oxygen through the solution. The amount of oxygen that is taken up by the composition also depends on the amount of sterols or cholesterol comprised in the composition. The amount of sterols in the liposomes, the amount of liposomes or both can be varied to reach optimal results with different tumors. In a preferred embodiment of the invention, the composition is enriched with oxygen. The composition comprises, e.g., at least 0.00475 g/L cholesterol, in particular at least 0.00525 g/L cholesterol, and is enriched with oxygen. Preferably, oxygen is bubbled through the composition until it is saturated with oxygen. Optimal, minimal and maximal amounts of cholesterol and of oxygen can easily be tested for different tumor tissues.
Preparation of the Composition
U.S. Provisional Patent Application No. 60/469,200 discloses that the compositions used in the methods of the present invention can be used to preserve the viability of organs and tissues.
The compositions for use in the invention are generally produced by a two-step process. The first step is to prepare a pre-mix for the first phase, which is the above-described base nutritive medium, designated as Premix-I, herein, and to prepare a premix for the second phase, designated as Premix-II, herein, in which the desired components are premixed, dissolved and/or suspended in water. The Premix-II composition is then processed through a microfluidizer or similar such apparatus, under conditions effective to provide a finely divided emulsion, e.g. a nanoparticle-scale emulsion. The resulting emulsion composition is then mixed with Premix-I, which provides various trace nutrients, and other components, to complete the production of the inventive composition.
Preparation of the Premix Compositions
Tables 1-4, below, summarize the preferred components and weight ranges for Premix I and Premix II, listed together. The components listed by Table 1-4 are the quantities found in one liter of the final composition, after all processing is completed. These components are sorted into these tables for convenience of description, in order to group the components by the way in which the composition is prepared in the examples discussed herein below. Unless otherwise indicated, all quantities shown in Tables 1-4 are in grams per liter of the final composition, i.e. the composition that includes both the aqueous phase and the emulsion phase.
Component quantities set forth by Tables 1-4 are based upon a total batch volume of 1 liter. As exemplified herein, the 1 liter batch volume is the end volume after both Premix-I and Premix-II are combined, wherein Premix-II has been processed into a microscale or nanoscale emulsion. The artisan will appreciate that the processes described are readily scaled up or down for smaller or larger batch sizes, depending on need.
All chemicals used in the preparation of the composition are of substantial purity and available from numerous commercial suppliers of biochemicals. Preferably, these are of USP grade or equivalent. Water should be WFI (Water for injection) grade, preferably USP grade. The artisan will appreciate that the employed chemicals are optionally substituted by substantially equivalent chemicals demonstrating the same purity and activity.
TABLE 1g/LSubstance- CONCENTRATION -Adenine HCl0.00019-0.00021B-120.00065-0.0007 Biotin0.00000038-0.00000042Cupric Sulfate0.00000124-0.00000137Ferric Nitrate0.000048-0.000053Ferric Sulfate0.00048-0.00053Putrescine HCl0.000077-0.000085Pyridoxine HCl0.000029-0.000033Riboflavin 0.00021-0.000231Thymidine0.00035-0.00039Zinc Sulfate 0.00041-0.000454
TABLE 2Ag/LSubstance- CONCENTRATION -Adenosine0.950-1.050Adenosine 5′ Monophosphate0.0019-0.0021Adenosine Triphosphate0.0019-0.0021Allopurinol0.133-0.147B′Nicotinamide Adenine Dinucleotide0.038-0.042PhosphateB′Nicotinamide Adenine Dinucleotide0.0019-0.0021Calcium Chloride0.152-0.168Choline Chloride0.0085-0.0094Chondrotin Sulfate0.0038-0.0042Cocarboxylase0.038-0.042Coenzyme A 0.0095-0.00105Cyclodextrin0.475-0.525Deoxyadenosine0.038-0.042Deoxycytidine0.038-0.042Deoxyguanosine0.038-0.042Dextran 7033.25-36.75Flavin Adenine Dinucleotide0.038-0.042Folic Acid0.0026-0.0028Glucose3.800-4.200Glutathione0.950-1.050Glycine0.0179-0.0197
TABLE 2Bg/LSubstance- CONCENTRATION -Heparin0.171-0.189HEPES3.396-3.753Hypoxanthine 0.002-0.0022Inositol0.0124-0.137 Insulin0.0095-0.0105L-Alanine0.00428-0.00473L-Arginine0.141-0.155L-Asparagine0.0076-0.0084L-Aspartic Acid0.064-0.070L-Cysteine0.0297-0.0329L-Cystine0.0167-0.0185L-Glutamic Acid 0.007-0.0078L-Glutamine4.750-5.250L-Histidine0.030-0.033L-Isoleucine 0.052-0.0572L-Leucine0.057-0.063L-Lysine0.0095-0.0105L-Methionine0.019-0.021L-Phenylalanine0.0337-0.0373L-Proline0.0164-0.0182L-Serine 0.025-0.0276L-Threonine0.051-0.056
TABLE 2Cg/LSubstance- CONCENTRATION -L-Tryptophan 0.009-0.0095L-Tyrosine0.053-0.059L-Valine0.050-0.055Magnesium Chloride 0.058-0.0643Magnesium Sulfate0.0475-0.0525Mannose3.135-3.465Niacinamide0.0019-0.0021Panthothenic Acid0.0021-0.0024Potassium Chloride0.296-0.328Pyridoxal HCl0.0019-0.0021Pyruvic Acid0.209-0.231Sodium Bicarbonate1.140-1.260Sodium Chloride6.650-7.350Sodium Phosphate Dibasic0.0676-0.0748Sodium Phosphate Monobasic0.0516-0.0570Thiamne0.0021-0.0023Transferrin0.00475-0.00525Uridine0.038-0.042Uridine Triphosphate0.038-0.042Yeastolate Ultra-Filtered (Sigma  38-42 mLChemical Company, Cat. No. Y2000)
TABLE 3g/LSubstance- CONCENTRATION -L-Cystine0.0167-0.0185L-Tyrosine0.053-0.059
TABLE 4g/LSubstance- CONCENTRATION -Cholesterol0.00475-0.00525Cod Liver Oil0.00095-0.00105Epithelial Growth Factor0.00000285-0.00000315Hepatocyte Growth Factor0.0000048-0.0000053Hydrocortisone0.00095-0.00105Linoleic Acid0.00095-0.00105Linolenic Acid0.00095-0.00105Oleic Acid0.00095-0.00105Phosphatidylcholine0.6%Platelet Derived Endothelial Growth Factor0.00000095-0.00000105Pluronic F-680.950-1.050Prostaglandin E1 0.000042-0.0000263Triiodo-L-Thyroxine0.00000475-0.0000053 TWEEN 80 ®0.002375-0.002625Vascular Endothelial Growth Factor 0.0000046-0.00000525Vitamin E0.0019-0.0021Process for Making Premix-I
Premix-I is prepared by dissolving or dispersing components in an order that is effective to achieve a uniform and clear aqueous composition, while avoiding undesirable reactions or the formation of insoluble complexes. For this reason, the components in Premix-I are preferably not mixed together until all are fully dissolved or dispersed in water. Preferably, as exemplified herein, the components listed by Tables 1, 2A-2C and Table 3 are processed into three different starting solutions, respectively, although the artisan will appreciate that this base composition is optionally prepared by variations on the exemplified scheme.
The starting solutions are then combined to prepare Premix-I, which constitutes phase 1, i.e. the non-emulsion base nutritive medium.
Process for Making Premix-II
Premix-II includes the emulsion-forming components of the composition. Broadly, these include the hydrophilic layer of the resulting emulsion particle, e.g., components that it is desired to deliver intracellularly. Premix-II also includes the components that form the hydrophobic layer of the resulting emulsion particle, e.g. a lipophilic outer layer that is supposed to allow fusion with living cell membranes for delivery of the hydrophilic core contents, including supportive endocrine factors, suitable agents to aid emulsification, e.g. wetting agent(s) and/or a block copolymer detergent, as well as hydrophobic phase components, such as cholesterol and/or phosphorous derived lipids. Preferably, these are as listed by Table 4, supra and are combined as described by the Examples below.
Microfluidation
The technique of high pressure homogenization, at pressures at or above 5000 psi (344750 hPa) is art-known as “microfluidation”. This process was used to create liposomes or nanoparticles with a uniform size distribution of a mean diameter of less than 200 nm. In addition to microfluidation, other standard emulsification methods are optionally employed, e.g. sonication, valve homogenization [Thornberg E. and Lundh, G. (1978) J. Food. Sci. 43:1553] and blade stirring, etc. Desirably, a water soluble surfactant, preferably an amphiphilic block copolymer with a molecular weight of several thousand Daltons, such as a polypropyleneoxide-polyethyleneoxide block copolymer surfactant (e.g. Pluronic F68) and/or TWEEN 80, is added to the aqueous solution in order to stabilize the coated particles against aggregation as they form. The surfactant also serves to enhance the effect of (ultra)sonication, if that method is employed.
A preferred apparatus for microfluidation as exemplified is the Microfluidizer No. HC5000V (Microfluidics Corp., Newton, Mass.) using compressed air supplied by an encapsulated air compressor, e.g. No. ES-6 from Sullair-Solutions (Michigan City, Ind.). The above-described apparatus employs high pressure and high shear homogenization to treat and emulsify the Premix-II composition.
In brief, the Premix-II composition, was processed by high pressure homogenization using the microfluidizer. The Premix-II was added to the microfluidizer reservoir in a continuous fashion, and forced through the specially designed cavitation or interaction chamber, where high shear stress and cavitation forces formed a highly divided emulsion. Through multiple cycles the mean droplet or liposome size, distribution, and combination of ingredients yielded the desired end product, e.g., the preferred nanoparticles.
Further details of the operation of the microfluidizer Model No. HC5000V are provided by the manufacturer's operating manual, available from Microfluidics Corporation, as Cat. No. 85.0112.